1. Field of the Invention
This invention relates to transparent specimen slides for use in microscopic examination of biological samples and, more particularly, to a microscope slide having precision projections for accurate control of specimen thickness.
2. Description of the Prior Art
In the prior art various attempts have been made to control the placement and thickness of biological samples such as blood on a microscope object slide. These include providing a recessed sample chamber in the slide, providing one or more grooves in the slide for containing the sample preparation and providing a recess in the cover plate. One such technique is illustrated and described in a British Pat. No. 679,791 to Knowles, dated Sept. 24, 1952 in which a spiral microgroove is provided in the surface of the microscope object slide to contain a fluid sample preparation such as diluted blood in a manner which causes the blood cells to line up along the spiral groove in a single layer for subsequent scanning. A cover plate is applied over the grooved microscope object slide so that the depth of the grooves will define the thickness of the fluid sample to be examined.
None of the known prior art efforts to produce a microscope object slide for the examination of a fluid biological sample with a precise sample thickness in the micron dimensional range, however, have been able to overcome drawbacks associated with the surface tension in the fluid sample. When the cover plate is applied to a slide of any prior art embodiments, the surface tension in the fluid sample prevents all of the excess sample from being squeezed from between the cover plate and the slide base and prevents an accurately spaced parallel fit between the cover plate and the slide base. Thus, the cover plate tends to ride on the fluid of the sample rather than on the portions of the base slide which define the parameters of the particular sample-containing cavity involved.